Code C28 STVA circuit tests good - Suzuki GSX-R Motorcycle Forums Gixxer.com

 
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post #1 of 12 (permalink) Old 06-28-2019, 12:40 AM Thread Starter
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Code C28 STVA circuit tests good

So a little back story. I dumped my bike last week. Long story short, went wide on a turn, there was no shoulder, the bike slipped down a drop off, I tried steering into it to get it to go back up the hill. The bike bit into the soft dirt and flung me over the handlebars. it fell over and some of it was under water. the right side, Entirely possible the stva got wet.

Stood the bike up and rode it 25 miles home. Cleaned it off the next day and and rode it again with no issues. Day 3 after the dump i gave it a real good washing and pulled it back into the garage. Day 4 I pull out of the garage and immediately have a code, and high idle. about 2k

Beought it home. C28. I just tested the pins and the ecu pins and got ~7.2 across all circuits, but the secondary butterflies are wide open. When I turn the bike on, and the fuel pump primes, they dont move. I tried wiggling them lightly while turning the bike on and nothing.

Is there another test I can do? Can I take the stva apart without breaking it and see if there is moisture in there? Not sure what to do here. I obviously dont want to buy another one unless i have to...

2007 GSXR 750
PC III, Quick Shift, Yosh TRC-d Full System

1981 gs550t
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post #2 of 12 (permalink) Old 06-28-2019, 04:31 AM
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Re: Code C28 STVA circuit tests good

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I just tested the pins and the ecu pins and got ~7.2 across all circuits, but the secondary butterflies are wide open.
What exactly did you measure and how? Do I understand correctly that you measured the pin pairs marked A/B and C/D on the STVA connector and found them to have 7.2Ω resistance and that you also measured the respective pairs of leads on the ECU side (pins 1/18 and 2/19, with the STVA coupler connected) and found the same resistance there?
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post #3 of 12 (permalink) Old 06-28-2019, 01:32 PM Thread Starter
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Re: Code C28 STVA circuit tests good

Correct
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post #4 of 12 (permalink) Old 06-28-2019, 02:25 PM
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Re: Code C28 STVA circuit tests good

See this and this.
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post #5 of 12 (permalink) Old 06-28-2019, 03:33 PM Thread Starter
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Re: Code C28 STVA circuit tests good

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What exactly did you measure and how? Do I understand correctly that you measured the pin pairs marked A/B and C/D on the STVA connector and found them to have 7.2Ω resistance and that you also measured the respective pairs of leads on the ECU side (pins 1/18 and 2/19, with the STVA coupler connected) and found the same resistance there?
This is exactly correct.

When powering the bike on, the butterlfies remain fully open. The is no clicking, grinding, nothing. No visible or audible attempt to move the butterflies.

For shits and giggles, I also unplugged the stps and made sure there was no moisture, or dirt in the harness. It was clean and dry. As was the stva wire harness. There is no signs of mud or moisture inside the frame so I feel relatively confident it did not in fact come in contact with water while laying on its side.

Last edited by maniac1886; 06-28-2019 at 03:38 PM.
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post #6 of 12 (permalink) Old 06-28-2019, 03:36 PM Thread Starter
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Re: Code C28 STVA circuit tests good

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See this and this.
Thanks @BillV

Your second link provides the steps I have followed last night to test the stva circuit. I got an expected resistance across both circuits, both at the stva wire harness connector and on the corresponding pins of the ecu harness connector

I fear the first link may end up being the route I have to take. Im really just hoping for some good news or ideas I havent thought of yet.


PS I cant solder. Im terrible at it.
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post #7 of 12 (permalink) Old 06-28-2019, 10:07 PM Thread Starter
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Re: Code C28 STVA circuit tests good

seems i've read something on here that @TheGeek is quite the stva professional....
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post #8 of 12 (permalink) Old 07-01-2019, 05:03 AM
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Re: Code C28 STVA circuit tests good

If you can read the resistance of the motor windings both at the STVA'a coupler, as well as at the ECU end, then it would seem like the motor and associated wiring are okay. If you don't see anything wrong in the ECU coupler, at or near the pins concerned, that might be breaking the connection, the ECU may have failed internally (although I can't imagine how that would happen, since I would expect any water-induced shorts to have a resistance much higher than the 7Ω of the motor windings).

Have a careful look at the connector and test with another ECU if you have access to one. Did any water make its way to the ECU connector itself?
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post #9 of 12 (permalink) Old 07-01-2019, 06:53 AM
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Re: Code C28 STVA circuit tests good

With the key off, can you move the secondaries by hand? The STVA housing is vented. If your STVA went under water, it's probably bad news. If water gets inside, the core of the STVA is a stepper motor and is iron. They rust incredibly fast. Your timeline of the events is pointing in this direction. I've seen some that are so rusted, the motor wouldn't even come apart. Others were rusted just enough to seize but could be cleaned up and soaked with WD-40 to stop the rust. If you can't move it with the key off, this is probably what you're in for.


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post #10 of 12 (permalink) Old 07-01-2019, 05:58 PM Thread Starter
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Re: Code C28 STVA circuit tests good

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Have a careful look at the connector and test with another ECU if you have access to one. Did any water make its way to the ECU connector itself?
No that part of the bike was up out of the water. No way it got wet in the fall.

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With the key off, can you move the secondaries by hand? The STVA housing is vented. If your STVA went under water, it's probably bad news. If water gets inside, the core of the STVA is a stepper motor and is iron. They rust incredibly fast. Your timeline of the events is pointing in this direction. I've seen some that are so rusted, the motor wouldn't even come apart. Others were rusted just enough to seize but could be cleaned up and soaked with WD-40 to stop the rust. If you can't move it with the key off, this is probably what you're in for.

I can not move the butterflies. I was afraid to apply too much pressure though. I assume you mean I would need to disassemble the stva assembly and soak just the stepper motor? I assume the motor would need to be disassembled so that any electrical connections dont get wet? This may be the case. It doesnt look like it go wet, but it was 4 days of relatively hot weather before I pulled the air box so I suppose it could have dried up first. There was no residual moisture in the connector though. I figure if water were to stay anywhere it would be inside that plug.

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post #11 of 12 (permalink) Old 07-02-2019, 06:57 AM
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Re: Code C28 STVA circuit tests good

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I can not move the butterflies. I was afraid to apply too much pressure though. I assume you mean I would need to disassemble the stva assembly and soak just the stepper motor? I assume the motor would need to be disassembled so that any electrical connections dont get wet? This may be the case. It doesnt look like it go wet, but it was 4 days of relatively hot weather before I pulled the air box so I suppose it could have dried up first. There was no residual moisture in the connector though. I figure if water were to stay anywhere it would be inside that plug.
The plug itself is sealed, so it wouldn't get water in it regardless. WD is non-conductive so you don't have to worry about the electrical connections. It's a bit more involved than just soaking it down.
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post #12 of 12 (permalink) Old 07-30-2019, 03:29 PM Thread Starter
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Re: Code C28 STVA circuit tests good

Big thanks to @TheGeek I finally got around to fixing the stva issue. It was in fact rusted. I took it all apart, cleaned it all up, reassembled it and it works again!
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